In an era of increasingly frequent interactions of information, requirements for servers that provide data services such as data processing and data storage have become more stringent. As the number of users increases, data information of such a massive number of users also grows continuously, and thus the load pressure of the servers increases. The load pressure of the servers can be reduced by upgrading the configuration of the servers. However, the service capability of a single server is ultimately limited. Under these circumstances, a cluster technology emerges and becomes an effective solution. Using the cluster technology, the performance, reliability, and flexibility can be highly enhanced with a relatively low cost, and task scheduling is the core of the cluster technology. By assembling multiple servers into a server cluster to provide external services jointly, the server cluster can perform parallel computing using multiple servers, thus obtaining a very high computing speed while lowering the load pressure of each single server. The servers in the server cluster can back up each other, so that the server cluster can still operate normally when any one of the servers fails, thereby achieving the high availability of the server cluster. An example includes a Server Load Balancer (SLB) cluster provided by Aliyun, which is a typical server cluster. As shown in FIG. 1, an SLB service virtualizes multiple cloud servers (Node) resources located in a same region into a high-performance and high-availability cloud server pool (i.e., a server cluster) by setting a Virtual IP Address (VIP), and distributes sessions from client terminals to the cloud server pool according to a specified manner. Meanwhile, the SLB service checks a health status of each cloud server in the cloud server pool, and automatically isolate a cloud server in an abnormal state, thereby solving a single-point issue associated with a single cloud server, and improving an overall service capability of the cloud server pool. A SLB cluster is made up of three parts: a cloud server pool, a load balancing system, and a control system. The load balancing system thereof is used for distributing sessions of client terminals to available cloud servers in the cloud server pool, and the control system thereof is used for configuring and monitoring the load balancing system.
All current server clusters are high-availability server clusters formed by at least two servers, and have a load balancing function. For example, sessions from a same client terminal (a same IP address) are distributed to multiple servers in a server cluster. Furthermore, the current server clusters have high availability. Sessions on a server in a server cluster may be synchronized to other servers, and the sessions would be automatically switched to another server if that server fails, thus ensuring that the sessions may not be interrupted and terminated. However, since the number of sessions is synchronized among all servers in this type of server cluster, the number of sessions of the server cluster is equal to the number of sessions of a server in the server cluster, and the session capacity of the server cluster is limited by the session capacity of one server. Therefore, when this type of server cluster is expanded, only processing performance of the server cluster can be increased, and the number of sessions of the server cluster cannot be increased. When the number of sessions of the server cluster is insufficient, the only option is to establish a new server cluster to meet the demand of the increasing number of sessions. As the cost of establishing a new server cluster is relatively high, the cost of managing the server cluster is also increased correspondingly.